Polypropylene with broad molecular weight distribution

ABSTRACT

Propylene homopolymer having a melt flow rate MFR 2  (230° C.) at least 50 g/10 min, a Mw/Mn at least 12.0 and a xylene cold soluble content (XCS) of at least 2.8 wt.-%.

The present invention is directed to a new propylene homopolymer withbroad molecular weight distribution and its manufacture.

Polypropylene is used in many applications. Depending on its endapplications the properties of the polypropylene must be tailoredaccordingly. For instance for some end applications very high stiffnessand flowability are required.

WO 2011076611 A1 describes a heterophasic system. However the producthas low flowability and moderate stiffness.

WO 2010/089123 A1 defines a polypropylene material with a melt flow rateMFR₂ (230° C.) up 12 g/10 min. The molecular weight distribution (Mw/Mn)does not exceed 8.

WO 2011/117103 describes a propylene copolymer with rather lowstiffness. The melt flow rate is very low.

Accordingly there is still the demand to provide polypropylene materialwith exceptional high stiffness paired with high flowability.

The finding of the present invention is to provide a propylenehomopolymer with a melt flow rate MFR₂ (230° C.) of at least 50 g/10 minand a broad molecular weight distribution (Mw/Mn), i.e. of at least12.0.

Accordingly the present invention is directed in a first aspect to apropylene homopolymer having

-   (a) a melt flow rate MFR₂ (230° C.) measured according to ISO 1133    of at least 50 g/10 min;-   (b) a ratio of weight average molecular weight (Mw) to number    average molecular weight (Mn) [Mw/Mn] of at least 12.0; and-   (c) a xylene cold soluble content (XCS) determined according ISO    16152 (25° C.) of at least 2.8 wt.-%.

In one embodiment said propylene homopolymer is not α-nucleated,preferably not nucleated at all. In a preferred embodiment the propylenehomopolymer is α-nucleated.

In a second aspect the present invention is directed to a propylenehomopolymer having

-   (a) a melt flow rate MFR₂ (230° C.) measured according to ISO 1133    of at least 50 g/10 min;-   (b) a ratio of the complex viscosity eta* at 0.05 rad/sec to the    complex viscosity eta* at 300 rad/sec of at least 4.0; and-   (c) a xylene cold soluble content (XCS) determined according ISO    16152 (25° C.) of at least 2.8 wt.-%.

In one embodiment said propylene homopolymer is not α-nucleated,preferably not nucleated at all. In a preferred embodiment the propylenehomopolymer is α-nucleated.

It has been found that the propylene homopolymers according to thisinvention are featured by very high stiffness by keeping the melt flowrate MFR₂ (230° C.) on a high level.

In the following the invention will be described in more detail. Bothaspects indicated above are discussed together.

According to the present invention the expression “polypropylenehomopolymer” relates to a polypropylene that consists substantially,i.e. of at least 99.0 wt.-%, more preferably of at least 99.5 wt.-%, ofpropylene units. In another embodiment only propylene units aredetectable, i.e. only propylene has been polymerized.

One requirement of the propylene homopolymer according to this inventionis its rather high melt flow rate. Accordingly the propylene homopolymerhas an MFR₂ (230° C.) measured according to ISO 1133 of at least 50 g/10min, preferably in the range of 50 to 1000 g/10 min, more preferably inthe range of 60 to 500 g/10 min, still more preferably in the range of70 to 300 g/10 min.

Another requirement for the propylene homopolymer is its broad molecularweight distribution. In the present application the molecular weightdistribution is determined by the Gel Permeation Chromatography (GPC).The number average molecular weight (Mn) is an average molecular weightof a polymer expressed as the first moment of a plot of the number ofmolecules in each molecular weight range against the molecular weight.In effect, this is the total molecular weight of all molecules dividedby the number of molecules. The number average molecular weight (Mn) isvery sensitive to changes in the weight fractions of low molecularweight species. In turn, the weight average molecular weight (Mw) is thefirst moment of a plot of the weight of polymer in each molecular weightrange against molecular weight. The weight average molecular weight (Mw)is very sensitive to changes in number of large molecules in a givensample of a polymer. Finally the z-average molecular weight (Mz) givesinformation about the very high molecular weight species of the polymer.

Accordingly the propylene homopolymer according to this invention has aratio of weight average molecular weight (Mw) to number averagemolecular weight (Mn) [Mw/Mn] of at least 12.0, preferably in the rangeof 12.0 to 16.5, more preferably in the range of 12.5 to 16.0, stillmore preferably in the range of 13.0 to 15.7.

Additionally it is preferred that the propylene homopolymer has a ratioof z-average molecular weight (Mz) to weight average molecular weight(Mw) [Mz/Mw] of at least 6.0, more preferably of 6.0 to 12.0, still morepreferably in the range of 6.0 to 10.0, yet more preferably in the rangeof 6.5 to 9.7.

Additionally or alternatively to the previous paragraph the propylenehomopolymer has a ratio of z-average molecular weight (Mz) to numberaverage molecular weight (Mn) [Mz/Mn] at least 80, more preferably inthe range of 80 to 140, still more preferably in the range of 90 to 130.

Alternatively or additionally to the Gel Permeation Chromatography (GPC)method, the propylene homopolymer can be defined by its rheologybehaviour. Thus it is appreciated that the polypropylene has a ratio ofthe complex viscosity eta* at 0.05 rad/sec to the complex viscosity eta*at 300 rad/sec measured by dynamic rheology according to ISO 6271-10 at230° C. of at least 4.0, preferably of at least 6.0, still morepreferably in the range of 6.0 to 15.0, yet more preferably in the rangeof 7.0 to 14.0.

It is preferred that the propylene homopolymer according to thisinvention is featured by rather high cold xylene soluble (XCS) content,i.e. by a xylene cold soluble (XCS) of at least 2.5 wt.-%, like at least2.8 wt.-%. Accordingly the propylene homopolymer has preferably a xylenecold soluble content (XCS) in the range of 2.5 to 5.0 wt.-%, morepreferably in the range of 2.8 to 4.8 wt.-%, still more preferably inthe range of 3.0 to 4.5 wt.-%.

The amount of xylene cold solubles (XCS) additionally indicates that thepropylene homopolymer is preferably free of any elastomeric polymercomponent, like an ethylene propylene rubber. In other words, thepropylene homopolymer shall be not a heterophasic polypropylene, i.e. asystem consisting of a polypropylene matrix in which an elastomericphase is dispersed. Such systems are featured by a rather high xylenecold soluble content.

The amount of xylene cold solubles (XCS) additionally indicates that thepropylene homopolymer preferably does not contain elastomeric(co)polymers forming inclusions as a second phase for improvingmechanical properties. A polymer containing elastomeric (co)polymers asinsertions of a second phase would by contrast be called heterophasicand is preferably not part of the present invention. The presence ofsecond phases or the so called inclusions are for instance visible byhigh resolution microscopy, like electron microscopy or atomic forcemicroscopy, or by dynamic mechanical thermal analysis (DMTA).Specifically in DMTA the presence of a multiphase structure can beidentified by the presence of at least two distinct glass transitiontemperatures.

Accordingly it is preferred that the propylene homopolymer according tothis invention has no glass transition temperature below −30, preferablybelow −25° C., more preferably below −20° C.

On the other hand, in one preferred embodiment the propylene homopolymeraccording to this invention has a glass transition temperature in therange of −15 to 0° C., more preferably in the range of −12 to −2° C.These values apply in particular in case the propylene homopolymer isα-nucleated.

Further, the propylene homopolymer is preferably a crystalline. The term“crystalline” indicates that the propylene homopolymer has a rather highmelting temperature. Accordingly throughout the invention the propylenehomopolymer is regarded as crystalline unless otherwise indicated.Therefore the propylene homopolymer preferably has a melting temperatureof more than 158° C., i.e. of more than 158 to 168° C., more preferablyof at least 160° C., i.e. in the range of 160 to 168° C., still morepreferably in the range of 160 to 165° C.

Preferably the propylene homopolymer is isotactic. Accordingly it ispreferred that the propylene homopolymer has a rather high pentadconcentration (mmmm %) i.e. more than 93.0%, more preferably more than94.5%, like more than 94.5 to 97.5%, still more preferably at least95.0%, like in the range of 95.0 to 97.5%.

A further characteristic of the propylene homopolymer is the low amountof misinsertions of propylene within the polymer chain, which indicatesthat the propylene homopolymer is produced in the presence of aZiegler-Natta catalyst, preferably in the presence of a Ziegler-Nattacatalyst (ZN-C) as defined in more detail below. Accordingly thepropylene homopolymer is preferably featured by low amount of 2,1erythro regio-defects, i.e. of equal or below 0.4 mol.-%, morepreferably of equal or below than 0.2 mol.-%, like of not more than 0.1mol.-%, determined by ¹³C-NMR spectroscopy. In an especially preferredembodiment no 2,1 erythro regio-defects are detectable.

Due to the low amounts of regio-defects the propylene homopolymer isadditionally characterized by a high content of thick lamella. Thespecific combination of rather high mmmm pentad concentration and lowamount of regio-defects has also impact on the crystallization behaviourof the propylene homopolymer. Thus, the propylene homopolymer of theinstant invention is featured by long crystallisable sequences and thusby a rather high amount of thick lamellae. To identify such thicklamellae the stepwise isothermal segregation technique (SIST) is themethod of choice. Therefore, the propylene homopolymer can beadditionally or alternatively defined by the weight ratio of thecrystalline fractions melting in the temperature range of above 160 to180° C. to the crystalline fractions melting in the temperature range of90 to 160 [(>160-180)/(90-160)].

Thus it is preferred that

-   (a) the weight ratio of the crystalline fractions melting in the    temperature range of above 160 to 180° C. to the crystalline    fractions melting in the temperature range of 90 to 160    [(>160-180)/(90-160)] of the non-nucleated propylene homopolymer is    at least 1.30, more preferably in the range of 1.30 to 2.00, still    more preferably in the range of 1.50 to 1.80,    or-   (b) the weight ratio of the crystalline fractions melting in the    temperature range of above 160 to 180° C. to the crystalline    fractions melting in the temperature range of 90 to 160    [(>160-180)/(90-160)] of the α-nucleated propylene homopolymer is at    least 3.00, more preferably in the range of 3.00 to 4.20, still more    preferably in the range of 3.19 to 4.20, even more preferably in the    range of 3.19 to 4.00,    wherein said fractions are determined by the stepwise isothermal    segregation technique (SIST).

Like the crystalline fractions of the propylene homopolymer determinedby the stepwise isothermal segregation technique (SIST) also thecrystallization temperature depends on the crystalline form of thepolymer. Accordingly it is preferred that

(a) the crystallization temperature of the the non-nucleated propylenehomopolymer is at least 110° C., more preferably at least 112° C., stillmore preferably in the range of 110 to 125° C., like in the range of 112to 123° C.;

or

(b) the crystallization temperature of the α-nucleated propylenehomopolymer is at least 128° C., more preferably at least 130° C., stillmore preferably in the range of 128 to 138° C., like in the range of 130to 136° C.

The propylene homopolymer is further featured by high stiffness.Accordingly the instant propylene homopolymer has a high tensilemodulus, wherein said modulus depends on the crystalline form of thepolymer. Accordingly it is preferred that

(a) the tensile modulus (specimen moulded at 180° C.) of the thenon-nucleated propylene homopolymer is at least 1,950 MPa, morepreferably at least 2,000 MPa, still more preferably in the range of1,950 to 2,500 MPa, like in the range of 1,950 to 2,400 MPa;or(b) the tensile modulus (specimen moulded at 180° C.) of the α-nucleatedpropylene homopolymer is at least 2,150 MPa, more preferably at least2,200 MPa, still more preferably in the range of 2,150 to 2,600 MPa,like in the range of 2,200 to 2,500 MPa.

The propylene homopolymer (H-PP) according to this invention preferablycomprises, more preferably consists of, three fractions, namely a firstpropylene homopolymer fraction (H-PP1), a second propylene homopolymerfraction (H-PP2) and a third propylene homopolymer fraction (H-PP3).

Preferably the weight ratio between the first propylene homopolymerfraction (H-PP1) and the second propylene homopolymer fraction (H-PP2)[(H-PP1):(H-PP2)] is 70:30 to 40:60, more preferably 65:35 to 50:50.

Preferably the weight ratio between the second propylene homopolymerfraction (H-PP2) and the third propylene homopolymer fraction (H-PP3)[(H-PP2):(H-PP3)] is 95:5 to 50:50, more preferably 90:10 to 70:30.

Thus it is especially preferred that the propylene homopolymercomprises, preferably consist of,

-   (a) of the first propylene homopolymer fraction (H-PP1) is in the    range of 40 to 60 wt.-%, more preferably in the range of 45 to 60    wt.-%, yet more preferably in the range of 50 to 60 wt.-%,-   (b) of the second propylene homopolymer fraction (H-PP2) is in the    range of 25 to 59.0 wt.-%, more preferably in the range of 27 to 52    wt.-%, yet more preferably in the range of 28 to 45.5 wt.-%, and-   (c) of the third propylene homopolymer fraction (H-PP3) is in the    range of 1.0 to 15.0 wt.-%, more preferably in the range of 3.0 to    13.0 wt.-%, yet more preferably in the range of 4.5 to 12.0 wt.-%,    based on the total amount of the propylene homopolymer, preferably    based on the total amount of the first propylene homopolymer    fraction (H-PP1), the second propylene homopolymer fraction (H-PP2)    and third propylene homopolymer fraction (H-PP3) together.

Preferably the first propylene homopolymer fraction (H-PP1), the secondpropylene homopolymer fraction (H-PP2) and the third propylenehomopolymer fraction (H-PP3) differ in the melt flow rate MFR₂ (230°C.), more preferably differ in the melt flow rate MFR₂ (230° C.) by atleast 30 g/10 min, yet more preferably by at least 35 g/10 min.

Preferably the first propylene homopolymer fraction (H-PP1) has a highermelt flow rate MFR₂ (230° C.) than the second propylene homopolymerfraction (H-PP2) and the second propylene homopolymer fraction (H-PP2)has a higher melt flow rate MFR₂ (230° C.) than the third propylenehomopolymer fraction (H-PP3).

Accordingly it is especially preferred that

(a) the melt flow rate MFR₂ (230° C.) of the first propylene homopolymerfraction (H-PP1) is at least 4 times higher, preferably at least 5 timeshigher, more preferably 4 times to 8 times higher, still more preferably5 times to 8 times higher, than the melt flow rate MFR₂ (230° C.) ofsecond propylene homopolymer fraction (H-PP2);and/or(b) the melt flow rate MFR₂ (230° C.) of the second propylenehomopolymer fraction (H-PP2) is at least 1,000 times higher, preferablyat least 5,000 times higher, more preferably 1,000 times to 5,000,000times higher, still more preferably 5,000 times to 500,000 times higher,than the melt flow rate MFR₂ (230° C.) of third propylene homopolymerfraction (H-PP3).

Thus in one specific embodiment the propylene homopolymer according tothe present invention comprises, preferably consists of, the firstpropylene homopolymer fraction (H-PP1), the second propylene homopolymerfraction (H-PP2) and the third propylene homopolymer fraction (H-PP3)wherein

-   (a) the melt flow rate MFR₂ (230° C.) of the first propylene    homopolymer fraction (H-PP1) is at least 300 g/10 min, more    preferably in the range of 300 to 2,000 g/10 min, still more    preferably in the range of 400 to 1,500 g/10 min, like in the range    of 450 to 1,200 g/10 min;    and/or-   (b) the melt flow rate MFR₂ (230° C.) of the second propylene    homopolymer fraction (H-PP2) is in the range of 10.0 to below 300    g/10 min;    and/or-   (c) the melt flow rate MFR₂ (230° C.) of the third propylene    homopolymer fraction (H-PP3) is below 0.1 g/10 min, more preferably    in the range of 0.000001 to below 0.1 g/10 min, still more    preferably in the range of 0.00001 to 0.1 g/10 min, like in the    range of 0.00001 to 0.01 g/10 min

Thus it is preferred that the first propylene homopolymer fraction(H-PP1) and the second propylene homopolymer fraction (H-PP2) fulfilltogether the inequation (I), more preferably inequation (Ia),

$\begin{matrix}{10.0 \geq \frac{{MFR}\left( {H - {{PP}\; 1}} \right)}{{MFR}\left( {H - {{PP}\; 2}} \right)} \geq 2.0} & (I) \\{8.0 \geq \frac{{MFR}\left( {H - {{PP}\; 1}} \right)}{{MFR}\left( {H - {{PP}\; 2}} \right)} \geq 3.0} & ({Ia})\end{matrix}$whereinMFR (H-PP1) is the melt flow rate MFR₂ (230° C.) [g/10 min] of the firstpropylene homopolymer fraction (H-PP1),MFR (H-PP2) is the melt flow rate MFR₂ (230° C.) [g/10 min] of thesecond propylene homopolymer fraction (H-PP2).

Additionally or alternatively it is preferred that the second propylenehomopolymer fraction (H-PP2) and the third propylene homopolymerfraction (H-PP3) fulfill together the inequation (II), more preferablyinequation (IIa),

$\begin{matrix}{{5 \times 10^{6}} \geq \frac{{MFR}\left( {H - {{PP}\; 2}} \right)}{{MFR}\left( {H - {{PP}\; 3}} \right)} \geq 1000} & ({II}) \\{{5 \times 10^{5}} \geq \frac{{MFR}\left( {H - {{PP}\; 2}} \right)}{{MFR}\left( {H - {{PP}\; 3}} \right)} \geq 5000} & ({IIa})\end{matrix}$whereinMFR (H-PP2) is the melt flow rate MFR₂ (230° C.) [g/10 min] of thesecond propylene homopolymer fraction (H-PP2),MFR (H-PP3) is the melt flow rate MFR₂ (230° C.) [g/10 min] of the thirdpropylene homopolymer fraction (H-PP3).

Additionally or alternatively it is preferred that the first propylenehomopolymer fraction (H-PP1) and the propylene homopolymer (H-PP)fulfill together the inequation (III), more preferably inequation(IIIa), still more preferably inequation (IIIb),

$\begin{matrix}{20.0 \geq \frac{{MFR}\left( {H - {{PP}\; 1}} \right)}{{MFR}\left( {H - {{PP}\; 2}} \right)} \geq 2.5} & ({III}) \\{15.0 \geq \frac{{MFR}\left( {H - {{PP}\; 1}} \right)}{{MFR}\left( {H - {PP}} \right)} \geq 3.0} & ({IIIa}) \\{10.0 \geq \frac{{MFR}\left( {H - {{PP}\; 1}} \right)}{{MFR}\left( {H - {PP}} \right)} \geq 3.5} & ({IIIb})\end{matrix}$whereinMFR (H-PP1) is the melt flow rate MFR₂ (230° C.) [g/10 min] of the firstpropylene homopolymer fraction (H-PP1),MFR (H-PP) is the melt flow rate MFR₂ (230° C.) [g/10 min] of thepropylene homopolymer (H-PP).

Preferably the propylene homopolymer according to this invention isproduced as defined in more detail below.

Preferably the first propylene homopolymer fraction (H-PP1) is producedin the first polymerization reactor (R1) whereas the second propylenehomopolymer fraction (H-PP2) is produced in the second polymerizationreactor (R2). The third propylene homopolymer fraction (H-PP3) ispreferably produced in the third polymerization reactor (R3).

The propylene homopolymer as defined in the instant invention maycontain up to 5.0 wt.-% additives (except the α-nucleating agent asdefined in detail below), like antioxidants, slip agents andantiblocking agents. Preferably the additive content is below 3.0 wt.-%,like below 1.0 wt.-%.

As mentioned above in one preferred embodiment the propylene homopolymercomprises a α-nucleating agent. In another preferred embodiment thepropylene homopolymer is free of α-nucleating agents, more preferably isfree of any nucleating agents.

In case the propylene homopolymer comprises an α-nucleating agent, it ispreferred that it is free of β-nucleating agents. The α-nucleating agentis preferably selected from the group consisting of

-   (i) salts of monocarboxylic acids and polycarboxylic acids, e.g.    sodium benzoate or aluminum tert-butylbenzoate, and-   (ii) dibenzylidenesorbitol (e.g. 1,3:2,4 dibenzylidenesorbitol) and    C₁-C₈-alkyl-substituted dibenzylidenesorbitol derivatives, such as    methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or    dimethyldibenzylidenesorbitol (e.g. 1,3:2,4 di(methylbenzylidene)    sorbitol), or substituted nonitol-derivatives, such as    1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol,    and-   (iii) salts of diesters of phosphoric acid, e.g. sodium    2,2′-methylenebis (4, 6,-di-tert-butylphenyl) phosphate or    aluminium-hydroxy-bis[2,2′-methylene-bis(4,6-di-t-butylphenyl)phosphate],    and-   (iv) vinylcycloalkane polymer and vinylalkane polymer (as discussed    in more detail below), and-   (v) mixtures thereof.

Such additives are generally commercially available and are described,for example, in “Plastic Additives Handbook”, pages 871 to 873, 5thedition, 2001 of Hans Zweifel.

Preferably the propylene homopolymer contains up to 5 wt.-% of theα-nucleating agent. In a preferred embodiment, the propylene homopolymercontains not more than 200 ppm, more preferably of 1 to 200 ppm, morepreferably of 5 to 100 ppm of a α-nucleating agent, in particularselected from the group consisting of dibenzylidenesorbitol (e.g.1,3:2,4 dibenzylidene sorbitol), dibenzylidenesorbitol derivative,preferably dimethyldibenzylidenesorbitol (e.g. 1,3:2,4di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives,such as1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol,sodium 2,2′-methylenebis (4, 6,-di-tert-butylphenyl) phosphate,vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof.

In one preferred embodiment sodium 2,2′-methylenebis (4,6,-di-tert-butylphenyl) phosphate is used.

In the following the manufacture of the propylene homopolymer isdescribed in more detail.

Accordingly the present invention is directed to a process for themanufacture of propylene homopolymer (H-PP) in a sequentialpolymerization system comprising at least two polymerization reactors((R1) and (R2)) or at least three polymerization reactors ((R1), (R2)and (R3)) connected in series, like in a sequential polymerizationsystem consisting of two polymerization reactors (R1) and (R2) connectedin series or consisting of three polymerization reactors (R1), (R2) and(R3) connected in series, wherein the polymerization of propylene in theat least two polymerization reactors ((R1) and (R2)) or in the at leastthree polymerization reactors ((R1), (R2) and (R3)), like the twopolymerization reactors (R1) and (R2) or the three polymerizationreactors (R1), (R2) and (R3), takes place in the presence of

-   (a) a Ziegler-Natta catalyst (ZN-C) comprising a titanium compound    (TC) having at least one titanium-halogen bond, and an internal    donor (ID), both supported on a magnesium halide,-   (b) a co-catalyst (Co), and-   (c) an external donor (ED),-   wherein-   (i) the internal donor (ID) comprises at least 80 wt.-% of a    succinate;-   (ii) the molar-ratio of co-catalyst (Co) to external donor (ED)    [Co/ED] is 2 to 60;-   (iii) the molar-ratio of co-catalyst (Co) to titanium compound (TC)    [Co/TC] is 150 to 300; and-   (iv) optionally the molar-ratio of external donor (ED) to titanium    compound [ED/TC] is in the range of more than 5 to below 100,    preferably in the range of 20 to 70.

Preferably at least one of the two polymerization reactors ((R1) and(R2)) is a gas phase reactor, more preferably one of the twopolymerization reactors (R1) and (R2) is a loop reactor (LR) whereas theother of the two polymerization reactors (R1) and (R2) is a gas phasereactor (GR1), still more preferably the first polymerization reactor(R1) is a loop reactor (LR) and the second polymerization reactor (R2)is a gas phase reactor (GPR1). Accordingly in case the sequentialpolymerization system consists of two polymerization reactors (R1) and(R2) the first polymerization reactor (R1) is a loop reactor (LR) andthe second polymerization reactor (R2) is a first gas phase reactor(GPR1)

In case the sequential polymerization system comprises, like consist of,three polymerization reactors (R1), (R2) and (R3), at least one,preferably at least two, of the three polymerization reactors ((R1),(R2) and (R2)) is/are (a) gas phase reactors, more preferably one of thethree polymerization reactors (R1), (R2) and (R3) is a loop reactor (LR)whereas as the other two of the three polymerization reactors (R1), (R2)and (R3) are gas phase reactors (GR1) and (GR2), still more preferablythe first polymerization reactor (R1) is a loop reactor (LR), the secondpolymerization reactor is a first gas phase reactor (GPR1) and the thirdpolymerization reactor (R2) is a second gas phase reactor (GPR2).

Preferably the operating temperature in the first polymerization reactor(R1) is in the range of 70 to 85° C. and/or the operating temperature inthe second polymerization reactor (R2) and optional in the third reactor(R3) is in the range of 75 to 95° C.

It has been surprisingly found out that a propylene homopolymer (H-PP)produced according to the inventive process has a low residue content.Further the productivity of the applied catalyst is very high.Additionally with the inventive process a high molecular weightdistribution can be achieved.

In the following the invention will be described in more detail.

Preferably the propylene homopolymer according to this invention isproduced in a sequential polymerization system comprising at least threereactors, preferably consists of three reactors (R1), (R2) and (R23).

The term “sequential polymerization system” indicates that the propylenehomopolymer is produced in at least three reactors connected in series.Accordingly the present polymerization system comprises at least a firstpolymerization reactor (R1), a second polymerization reactor (R2), and athird polymerization reactor (R3). The term “polymerization reactor”shall indicate that the main polymerization takes place. Thus in casethe process consists of three polymerization reactors, this definitiondoes not exclude the option that the overall system comprises forinstance a pre-polymerization step in a pre-polymerization reactor. Theterm “consist of” is only a closing formulation in view of the mainpolymerization reactors.

Preferably the first polymerization reactor (R1) is a slurry reactor(SR), whereas the second polymerization reactor (R2) and the thirdpolymerization reactor (R3) are a gas phase reactors (GPRs). A gas phasereactor (GPR) according to this invention is preferably a fluidized bedreactor, a fast fluidized bed reactor or a settled bed reactor or anycombination thereof.

Accordingly, the first polymerization reactor (R1) is preferably aslurry reactor (SR) and can be any continuous or simple stirred batchtank reactor or loop reactor operating in bulk or slurry. Bulk means apolymerization in a reaction medium that comprises of at least 60% (w/w)monomer. According to the present invention the slurry reactor (SR) ispreferably a (bulk) loop reactor (LR). Accordingly the averageconcentration of propylene homopolymer, i.e. the first fraction (1^(st)F) of the propylene homopolymer (i.e. the first propylene homopolymerfraction (H-PP1)), in the polymer slurry within the loop reactor (LR) istypically from 15 wt.-% to 55 wt.-%, based on the total weight of thepolymer slurry within the loop reactor (LR). In one preferred embodimentof the present invention the average concentration of the firstpropylene homopolymer fraction (H-PP1) in the polymer slurry within theloop reactor (LR) is from 20 wt.-% to 55 wt.-% and more preferably from25 wt.-% to 52 wt.-%, based on the total weight of the polymer slurrywithin the loop reactor (LR).

Preferably the propylene homopolymer of the first polymerization reactor(R1), i.e. the first propylene homopolymer fraction (H-PP1), morepreferably the polymer slurry of the loop reactor (LR) containing thefirst propylene homopolymer fraction (H-PP1), is directly fed into thesecond polymerization reactor (R2), i.e. into the first gas phasereactor (GPR1), without a flash step between the stages. This kind ofdirect feed is described in EP 887379 A, EP 887380 A, EP 887381 A and EP991684 A. By “direct feed” is meant a process wherein the content of thefirst polymerization reactor (R1), i.e. of the loop reactor (LR), thepolymer slurry comprising the the first propylene homopolymer fraction(H-PP1), is led directly to the next stage gas phase reactor.

Alternatively, the propylene homopolymer of the first polymerizationreactor (R1), i.e. the first propylene homopolymer fraction (H-PP1),more preferably polymer slurry of the loop reactor (LR) containing thefirst propylene homopolymer fraction (H-PP1), may be also directed intoa flash step or through a further concentration step before fed into thesecond polymerization reactor (R2), i.e. into the first gas phasereactor (GPR1). Accordingly, this “indirect feed” refers to a processwherein the content of the first polymerization reactor (R1), of theloop reactor (LR), i.e. the polymer slurry, is fed into the secondpolymerization reactor (R2), into the first gas phase reactor (GPR1),via a reaction medium separation unit and the reaction medium as a gasfrom the separation unit.

More specifically, the second polymerization reactor (R2), and anysubsequent reactor, for instance the third polymerization reactor (R3),are preferably gas phase reactors (GPRs).

Such gas phase reactors (GPR) can be any mechanically mixed or fluid bedreactors. Preferably the gas phase reactors (GPRs) comprise amechanically agitated fluid bed reactor with gas velocities of at least0.2 msec. Thus it is appreciated that the gas phase reactor is afluidized bed type reactor preferably with a mechanical stirrer.

Thus in a preferred embodiment the first polymerization reactor (R1) isa slurry reactor (SR), like loop reactor (LR), whereas the secondpolymerization reactor (R2) and the third polymerization reactor (R3),are gas phase reactors (GPRs). Accordingly for the instant process atleast three polymerization reactors (R1), (R2) and (R3), namely a slurryreactor (SR), like loop reactor (LR) and a first gas phase reactor(GPR1) and a second gas phase reactor (GPR2), connected in series areused. If needed prior to the slurry reactor (SR) a pre-polymerizationreactor is placed.

The Ziegler-Natta catalyst (ZN-C) is fed into the first polymerizationreactor (R1) and is transferred with the polymer (slurry) obtained inthe first polymerization reactor (R1) into the subsequent reactors. Ifthe process covers also a pre-polymerization step it is preferred thatthe Ziegler-Natta catalyst (ZN-C) is fed in the pre-polymerizationreactor. Subsequently the pre-polymerization product containing theZiegler-Natta catalyst (ZN-C) is transferred into the firstpolymerization reactor (R1).

A preferred multistage process is a “loop-gas phase”-process, such asdeveloped by Borealis A/S, Denmark (known as BORSTAR® technology)described e.g. in patent literature, such as in EP 0 887 379, WO92/12182 WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 or inWO 00/68315.

A further suitable slurry-gas phase process is the Spheripol® process ofBasell.

Especially good results are achieved in case the temperature in thereactors is carefully chosen.

Accordingly it is preferred that the operating temperature in the firstpolymerization reactor (R1) is in the range of 70 to 85° C., morepreferably in the range of 70 to 82° C., still more preferably in therange of 72 to 80° C., like in the range of 73 to 80° C., i.e. 75° C.

Alternatively or additionally to the previous paragraph it is preferredthat the operating temperature in the second polymerization reactor (R2)is in the range of 70 to 95° C., more preferably in the range of 75 to90° C., still more preferably in the range of 75 to 85° C., like in therange of 78 to 82° C., i.e. 80° C.

Alternatively or additionally to the two previous paragraphs it ispreferred that the operating temperature in the third polymerizationreactor (R3) is in the range of 70 to 95° C., more preferably in therange of 75 to 90° C.

Typically the pressure in the first polymerization reactor (R1),preferably in the loop reactor (LR), is in the range of from 20 to 80bar, preferably 30 to 70 bar, like 35 to 65 bar, whereas the pressure inthe second polymerization reactor (R2), i.e. in the first gas phasereactor (GPR1), and in the third polymerization reactor (R3), e.g. inthe second gas phase reactor (GPR2), is in the range of from 5 to 50bar, preferably 15 to 35 bar.

Preferably hydrogen is added in each polymerization reactor in order tocontrol the molecular weight, i.e. the melt flow rate MFR₂.

Accordingly it is preferred that the hydrogen to propylene feed ratio[H₂/C₃] to the first polymerization reactor (R1) is in the range of 10to 60 mol/kmol, more preferably in the range of 15 to 50 mol/kmol,and/or the hydrogen to propylene feed ratio [H₂/C₃] to the secondpolymerization reactor (R2) is in the range of 10 to 260 mol/kmol, morepreferably in the range of 15 to 180 mol/kmol. In turn the hydrogen topropylene feed ratio [H₂/C₃] to the third reactor is in the range of 0to 20 mol/kmol, more preferably in the range of 0 to 5.0 mol/kmol. It isespecially preferred that the hydrogen and propylene feed are constantover the polymerization time.

The average residence time (τ) is defined as the ratio of the reactionvolume (V_(R)) to the volumetric outflow rate from the reactor (Q_(o))(i.e. V_(R)/Q_(o)), i.e τ=V_(R)/Q_(o) [tau=V_(R)/Q_(o)]. In case of aloop reactor the reaction volume (V_(R)) equals to the reactor volume.

The average residence time (τ) in the first polymerization reactor (R1)is preferably at least 20 min, more preferably in the range of 20 to 45min, still more preferably in the range of 22 to 42 min, like in therange of 22 to 40 min, and/or the average residence time (τ) in thesecond polymerization reactor (R2) is preferably at least 90 min, morepreferably in the range of 90 to 200 min, still more preferably in therange of 100 to 190 min, yet more preferably in the range of 105 to 180min. Preferably the average residence time (τ) in the thirdpolymerization reactor (R3) is at least 100 min, more preferably in therange of 100 to 300 min, still more preferably in the range of 120 to280 min.

Further it is preferred that the average residence time (τ) in the totalsequential polymerization system, more preferably that the averageresidence time (τ) in the first (R1) and second polymerization reactors(R2) and third polymerization reactor (R3) together, is at most 500 min,more preferably in the range of 210 to 500 min, still more preferably inthe range of 220 to 400 min, still more preferably in the range of 230to 380 min.

As mentioned above the instant process can comprises in addition to the(main) polymerization of the propylene homopolymer in the at least threepolymerization reactors (R1, R3 and R3) prior thereto apre-polymerization in a pre-polymerization reactor (PR) upstream to thefirst polymerization reactor (R1).

In the pre-polymerization reactor (PR) a polypropylene (Pre-PP) isproduced. The pre-polymerization is conducted in the presence of theZiegler-Natta catalyst (ZN-C). According to this embodiment theZiegler-Natta catalyst (ZN-C), the co-catalyst (Co), and the externaldonor (ED) are all introduced to the pre-polymerization step. However,this shall not exclude the option that at a later stage for instancefurther co-catalyst (Co) is added in the polymerization process, forinstance in the first reactor (R1). In one embodiment the Ziegler-Nattacatalyst (ZN-C), the co-catalyst (Co), and the external donor (ED) areonly added in the pre-polymerization reactor (PR), if apre-polymerization is applied.

The pre-polymerization reaction is typically conducted at a temperatureof 0 to 60° C., preferably from 15 to 50° C., and more preferably from20 to 45° C.

The pressure in the pre-polymerization reactor is not critical but mustbe sufficiently high to maintain the reaction mixture in liquid phase.Thus, the pressure may be from 6 to 100 bar, for example 10 to 70 bar.

In a preferred embodiment, the pre-polymerization is conducted as bulkslurry polymerization in liquid propylene, i.e. the liquid phase mainlycomprises propylene, with optionally inert components dissolved therein.Furthermore, according to the present invention, an ethylene feed isemployed during pre-polymerization as mentioned above.

It is possible to add other components also to the pre-polymerizationstage. Thus, hydrogen may be added into the pre-polymerization stage tocontrol the molecular weight of the polypropylene (Pre-PP) as is knownin the art. Further, antistatic additive may be used to prevent theparticles from adhering to each other or to the walls of the reactor.

The precise control of the pre-polymerization conditions and reactionparameters is within the skill of the art.

Due to the above defined process conditions in the pre-polymerization,preferably a mixture (MI) of the Ziegler-Natta catalyst (ZN-C) and thepolypropylene (Pre-PP) produced in the pre-polymerization reactor (PR)is obtained. Preferably the Ziegler-Natta catalyst (ZN-C) is (finely)dispersed in the polypropylene (Pre-PP). In other words, theZiegler-Natta catalyst (ZN-C) particles introduced in thepre-polymerization reactor (PR) split into smaller fragments which areevenly distributed within the growing polypropylene (Pre-PP). The sizesof the introduced Ziegler-Natta catalyst (ZN-C) particles as well as ofthe obtained fragments are not of essential relevance for the instantinvention and within the skilled knowledge.

As mentioned above, if a pre-polymerization is used, subsequent to saidpre-polymerization, the mixture (MI) of the Ziegler-Natta catalyst(ZN-C) and the polypropylene (Pre-PP) produced in the pre-polymerizationreactor (PR) is transferred to the first reactor (R1). Typically thetotal amount of the polypropylene (Pre-PP) in the final propylenehomopolymer (H-PP) is rather low and typically not more than 5.0 wt.-%,more preferably not more than 4.0 wt.-%, still more preferably in therange of 0.5 to 4.0 wt.-%, like in the range 1.0 of to 3.0 wt.-%.

In case that pre-polymerization is not used propylene and the otheringredients such as the Ziegler-Natta catalyst (ZN-C) are directlyintroduced into the first polymerization reactor (R1).

Accordingly the process according the instant invention comprises thefollowing steps under the conditions set out above

(a) in the first polymerization reactor (R1), i.e. in a loop reactor(LR), propylene is polymerized obtaining a first propylene homopolymerfraction (H-PP1) of the propylene homopolymer (H-PP),

(b) transferring said first propylene homopolymer fraction (H-PP1) to asecond polymerization reactor (R2),

(c) in the second polymerization reactor (R2) propylene is polymerizedin the presence of the first propylene homopolymer fraction (H-PP1)obtaining a second propylene homopolymer fraction (H-PP2) of thepropylene homopolymer (H-PP), said first propylene homopolymer fraction(H-PP1) and said second propylene homopolymer fraction (H-PP2) form afirst mixture (1^(st) M),(d) transferring said first mixture (1^(st) M) to the thirdpolymerization reactor (R3), and(e) in the third polymerization reactor (R3) propylene is polymerized inthe presence of the first mixture (1^(st) M) obtaining a third propylenehomopolymer fraction (H-PP3) of the propylene homopolymer (H-PP), saidfirst mixture (1^(st) M) and said propylene homopolymer fraction (H-PP3)form the propylene homopolymer (H-PP).

A pre-polymerization as described above can be accomplished prior tostep (a).

After the polymerization the propylene homopolymer is discharged andmixed with additives as mentioned above.

As mentioned above in the specific process for the preparation of thepropylene homopolymer as defined above a Ziegler-Nana catalyst (ZN-C)must be used. Accordingly the Ziegler-Natta catalyst (ZN-C) will be nowdescribed in more detail.

The Ziegler-Natta catalyst (ZN-C) comprises a titanium compound (TC),which has at least one titanium-halogen bond, and an internal donor(ID), both supported on magnesium halide, preferably in active form.

The internal donor (ID) used in the present invention comprises asuccinate. The internal donor (ID) may in addition to the succinatecomprise phthalate or a diether. The preferred internal donor (ID) is asuccinate or a mixture of a succinate and a phthalate. It is especiallypreferred that the internal donor (ID) is a succinate only.

Accordingly it is preferred that the internal donor (ID) comprisessuccinate of at least 80 wt.-%, more preferably at least 90 wt.-%, stillmore preferably at least 95 wt.-% and even more preferably at least 99wt.-%, of the total weight of the internal donor (ID). It is, however,preferred that the internal donor (ID) essentially consists, e.g. is, asuccinate.

The Ziegler-Natta catalyst comprising a succinate as defined above asinternal donor (ID) can for example be obtained by reaction of ananhydrous magnesium halide with an alcohol, followed by titanation witha titanium halide and reaction with the respective succinate. Such acatalyst comprises 2 to 6 wt.-% of titanium, 10 to 20 wt.-% of magnesiumand 5 to 30 wt.-% of internal donor (ID) with chlorine and solventmaking up the remainder.

Suitable succinates have the formula (I)

wherein R¹ to R⁴ are equal to or different from one another and arehydrogen, or a C₁ to C₂₀ linear or branched alkyl, alkenyl, cycloalkyl,aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms,and R¹ to R⁴, being joined to the same carbon atom, can be linkedtogether to form a cycle; and R⁵ and R⁶ are equal to or different fromone another and are a linear or branched alkyl, alkenyl, cycloalkyl,aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms.

Suitable phthalates are selected from the alkyl, cycloalkyl and arylphthalates, such as for example diethyl phthalate, diisobutyl phthalate,di-n-butyl phthalate, dioctyl phthalate, diphenyl phthalate andbenzylbutyl phthalate.

Suitable diethers are selected from 1,3-diethers of formula (II) or(III)

wherein in formula (II) and (III)R₁ and R₂ are the same or different and can be a linear or branchedC₁-C₁₂-alkyl, or R₁ withR₅ and/or R₂ with R₆ can form a ring with 4 to 6 C-atoms,R₃ and R₄ of formula (II) are the same or different and can be H or alinear or branched C₁-C₁₂-alkyl or R₃ and R₄ can form together a ringwith 5 to 10 C-atoms, which can be part of an aliphatic or aromaticpolycyclic ring system with 9 to 20 C-atoms,R₅ and R₆ in formula (I) are the same or different and can be H or alinear or branched C₁-C₁₂-alkyl or can form together an aliphatic ringwith 5 to 8 C-atoms,and R₅₁, R₆₁ and R₇ in formula (III) are the same or different and canbe H or a linear or branched C₁-C₁₂-alkyl or two or three of R₅₁, R₆₁and R₇ can form together with C₁ to C₃ an aromatic ring or ring systemwith 6 to 14 C-atoms, preferably 10 to 14 C-atoms, or mixturestherefrom.

A Ziegler-Natta catalyst (ZN-C) comprising a succinate as internal donor(ID) is commercially available for example from Basell under the AvantZN trade name. One particularly preferred Ziegler-Natta catalyst (ZN-C)is the catalyst ZN168M of Basell.

As further component in the instant polymerization process an externaldonor (ED) must be present. Suitable external donors (ED) includecertain silanes, ethers, esters, amines, ketones, heterocyclic compoundsand blends of these. It is especially preferred to use a silane. It ismost preferred to use silanes of the general formulaR^(a) _(p)R^(b) _(q)Si(OR^(c))_((4-p-q))wherein R^(a), R^(b) and R^(c) denote a hydrocarbon radical, inparticular an alkyl or cycloalkyl group, and wherein p and q are numbersranging from 0 to 3 with their sum p+q being equal to or less than 3.R^(a), R^(b) and R^(c) can be chosen independently from one another andcan be the same or different.

Accordingly a preferred external donor (ED) is represented by theformulaSi(OCH₃)₂R₂ ⁵wherein R5 represents a branched-alkyl group having 3 to 12 carbonatoms, preferably a branched-alkyl group having 3 to 6 carbon atoms, ora cyclo-alkyl having 4 to 12 carbon atoms, preferably a cyclo-alkylhaving 5 to 8 carbon atoms.

It is in particular preferred that R⁵ is selected from the groupconsisting of iso-propyl, iso-butyl, iso-pentyl, tert.-butyl,tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl andcycloheptyl.

Another preferred external donor (ED) is is represented by the formulaSi(OCH₂CH₃)₃(NR^(x)R^(y))wherein R^(x) and R^(y) can be the same or different a represent ahydrocarbon group having 1 to 12 carbon atoms.

R^(x) and R^(y) are independently selected from the group consisting oflinear aliphatic hydrocarbon group having 1 to 12 carbon atoms, branchedaliphatic hydrocarbon group having 1 to 12 carbon atoms and cyclicaliphatic hydrocarbon group having 1 to 12 carbon atoms. It is inparticular preferred that R^(x) and R^(y) are independently selectedfrom the group consisting of methyl, ethyl, n-propyl, n-butyl, octyl,decanyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl, tert.-amyl,neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.

More preferably both R^(x) and R^(y) are the same, yet more preferablyboth R^(x) and R^(y) are an ethyl group.

Specific examples of such silanes are (tert-butyl)₂Si(OCH₃)₂, cylohexylmethyl dimethoxy silan (cyclohexyl)(methyl)Si(OCH₃)₂ (referred to as “Cdonor”), (phenyl)₂Si(OCH₃)₂, dicyclopentyl dimethoxy silane(cyclopentyl)₂Si(OCH₃)₂ (referred to as “D donor”) anddiethylaminotriethoxysilane (CH₃CH₂)₂NSi(OCH₂CH₃)₃ (referred to as“U-donor”).

The co-catalyst is preferably a compound of group 13 of the periodictable (IUPAC), e.g. organo aluminum, such as an aluminum compound, likealuminum alkyl, aluminum halide or aluminum alkyl halide compound.Accordingly in one specific embodiment the co-catalyst (Co) is atrialkylaluminium, like triethylaluminium (TEAL), dialkyl aluminiumchloride or alkyl aluminium sesquichloride. In one specific embodimentthe co-catalyst (Co) is triethylaluminium (TEAL).

Advantageously, the trialkylaluminium, like triethylaluminium (TEAL) hasa hydride content, expressed as AlH₃, of less than 1.0 wt % with respectto the trialkylaluminium, like the triethyl aluminium (TEAL). Morepreferably, the hydride content is less than 0.5 wt %, and mostpreferably the hydride content is less than 0.1 wt %.

To obtain best the desired propylene homopolymer of the presentinvention the ratio between on the one hand of co-catalyst (Co) and theexternal donor (ED) [Co/ED] and on the other hand of the co-catalyst(Co) and the titanium compound (TC) [Co/TC] must be carefully chosen.

Accordingly

(a) the mol-ratio of co-catalyst (Co) to external donor (ED) [Co/ED]must be in the range of 2 to 60, preferably is in the range of 2 to 10,more preferably is in the range of 3 to 8, still more preferably is inthe range of 4 to 7; and

(b) the mol-ratio of co-catalyst (Co) to titanium compound (TC) [Co/TC]must be in the range of 150 to 300, preferably is in the range of 170 to280, more preferably is in the range of 190 to 270, still morepreferably is in the range of 230 to 260.

It is especially preferred that the molar-ratio of external donor (ED)to titanium compound [ED/TC] is in the range of more than 5 to below100, more preferably in the range of 20 to 70.

In the following the present invention is further illustrated by meansof examples.

EXAMPLES

A. Measuring Methods

The following definitions of terms and determination methods apply forthe above general description of the invention including the claims aswell as to the below examples unless otherwise defined.

Quantification of Microstructure by NMR Spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used toquantify the isotacticity and regio-regularity of the polypropylenehomopolymers.

Quantitative ¹³C {¹H} NMR spectra were recorded in the solution-stateusing a Bruker Advance III 400 NMR spectrometer operating at 400.15 and100.62 MHz for ¹H and ¹³C respectively. All spectra were recorded usinga ¹³C optimised 10 mm extended temperature probehead at 125° C. usingnitrogen gas for all pneumatics.

For polypropylene homopolymers approximately 200 mg of material wasdissolved in 1,2-tetrachloroethane-d₂ (TCE-d₂). To ensure a homogenoussolution, after initial sample preparation in a heat block, the NMR tubewas further heated in a rotatary oven for at least 1 hour. Uponinsertion into the magnet the tube was spun at 10 Hz. This setup waschosen primarily for the high resolution needed for tacticitydistribution quantification (Busico, V., Cipullo, R., Prog. Polym. Sci.26 (2001) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M.,Segre, A. L., Macromolecules 30 (1997) 6251). Standard single-pulseexcitation was employed utilising the NOE and bi-level WALTZ16decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong,R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225;Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J.,Talarico, G., Macromol. Rapid Commun. 2007, 28, 11289). A total of 8192(8k) transients were acquired per spectra.

Quantitative ¹³C {¹H} NMR spectra were processed, integrated andrelevant quantitative properties determined from the integrals usingproprietary computer programs.

For polypropylene homopolymers all chemical shifts are internallyreferenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

Characteristic signals corresponding to regio defects (Resconi, L.,Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang,W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N.,Macromolecules 17 (1984), 1950) or comonomer were observed.

The tacticity distribution was quantified through integration of themethyl region between 23.6-19.7 ppm correcting for any sites not relatedto the stereo sequences of interest (Busico, V., Cipullo, R., Prog.Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G.,Vacatello, M., Segre, A. L., Macromolecules 30 (1997) 6251).

Specifically the influence of regio-defects and comonomer on thequantification of the tacticity distribution was corrected for bysubtraction of representative regio-defect and comonomer integrals fromthe specific integral regions of the stereo sequences.

The isotacticity was determined at the pentad level and reported as thepercentage of isotactic pentad (mmmm) sequences with respect to allpentad sequences: [mmmm]%=100*(mmmm/sum of all pentads)

The presence of 2,1 erythro regio-defects was indicated by the presenceof the two methyl sites at 17.7 and 17.2 ppm and confirmed by othercharacteristic sites. Characteristic signals corresponding to othertypes of regio-defects were not observed (Resconi, L., Cavallo, L.,Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

The amount of 2,1 erythro regio-defects was quantified using the averageintegral of the two characteristic methyl sites at 17.7 and 17.2 ppm:P _(21e)=(I _(e6) +I _(e8))/2

The amount of 1,2 primary inserted propene was quantified based on themethyl region with correction undertaken for sites included in thisregion not related to primary insertion and for primary insertion sitesexcluded from this region:P ₁₂ =I _(CH3) +P _(12e)

The total amount of propene was quantified as the sum of primaryinserted propene and all other present regio-defects:P _(total) =P ₁₂ +P _(21e)

The mole percent of 2,1 erythro regio-defects was quantified withrespect to all propene:[21e]mol.-%=100(P _(21e) /P _(total))

Calculation of melt flow rate MFR₂ (230° C.) of the second propylenehomopolymer fraction (H-PP2):

$\begin{matrix}{{{MFR}\left( {{PP}\; 2} \right)} = 10^{\lbrack\frac{{\log{({{MFR}{({PP})}})}} - {{w{({{PP}\; 1})}} \times {\log{({{MFR}{({{PP}\; 1})}})}}}}{w{({{PP}\; 2})}}\rbrack}} & (I)\end{matrix}$

-   wherein-   w(PP1) is the weight fraction [in wt.-%] of the first propylene    homopolymer fraction (H-PP1),-   w(PP2) is the weight fraction [in wt.-%] of the second propylene    homopolymer fraction (H-PP2),-   MFR(PP1) is the melt flow rate MFR₂ (230° C.) [in g/10 min] of the    first propylene homopolymer fraction (H-PP1),-   MFR(PP) is the melt flow rate MFR₂ (230° C.) [in g/10 min] of the    propylene homopolymer obtained after the second polymerization    reactor (R2), i.e. of the mixture of the first propylene homopolymer    fraction (H-PP1) and second propylene homopolymer fraction (H-PP2),-   MFR(PP2) is the calculated melt flow rate MFR₂ (230° C.) [in g/10    min] of the second propylene homopolymer fraction (H-PP2).

Calculation of melt flow rate MFR₂ (230° C.) of the third propylenehomopolymer fraction (H-PP3):

$\begin{matrix}{{{MFR}\left( {{PP}\; 3} \right)} = 10^{\lbrack\frac{{\log{({{MFR}{({PP})}})}} - {{w{({{PP}\; 2})}} \times {\log{({{MFR}{({{PP}\; 2})}})}}}}{w{({{PP}\; 3})}}\rbrack}} & ({II})\end{matrix}$

-   wherein-   w(PP2) is the weight fraction [in wt.-%] of the propylene    homopolymer obtained after the second polymerization reactor (R2),    i.e. of the mixture of the first propylene homopolymer fraction    (H-PP1) and second second propylene homopolymer fraction (H-PP2),-   w(PP3) is the weight fraction [in wt.-%] of the third propylene    homopolymer fraction (H-PP3),-   MFR(PP2) is the melt flow rate MFR₂ (230° C.) [in g/10 min] of the    propylene homopolymer obtained after the second polymerization    reactor (R2), i.e. of the mixture of the first propylene homopolymer    fraction (H-PP1) and second propylene homopolymer fraction (H-PP2),-   MFR(PP) is the melt flow rate MFR₂ (230° C.) [in g/10 min] of the    propylene homopolymer obtained after the third polymerisation    reactor (R3), i.e. of the mixture of the first propylene homopolymer    fraction (H-PP1), the second propylene homopolymer fraction (H-PP2)    and the third propylene homopolymer fraction (H-PP3),-   MFR(PP3) is the calculated melt flow rate MFR₂ (230° C.) [in g/10    min] of the third propylene homopolymer fraction (H-PP3).

MFR₂ (230° C.) is measured according to ISO 1133 (230° C., 2.16 kg load)

Number average molecular weight (M_(n)), weight average molecular weight(M_(w)), z-average molecular weight (M_(x))

Molecular weight averages Mw, Mn and Mz were determined by GelPermeation Chromatography (GPC) according to ISO 16014-4:2003 and ASTM D6474-99. A PolymerChar GPC instrument, equipped with infrared (IR)detector was used with 3× Olexis and 1× Olexis Guard columns fromPolymer Laboratories and 1,2,4-trichlorobenzene (TCB, stabilized with250 mg/L 2,6-Di tert butyl-4-methyl-phenol) as solvent at 160° C. and ata constant flow rate of 1 mL/min. 200 μL of sample solution wereinjected per analysis. The column set was calibrated using universalcalibration (according to ISO 16014-2:2003) with at least 15 narrow MWDpolystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/mol.Mark Houwink constants for PS, PE and PP used are as described per ASTMD 6474-99. All samples were prepared by dissolving 5.0-9.0 mg of polymerin 8 mL (at 160° C.) of stabilized TCB (same as mobile phase) for 2.5hours for PP or 3 hours for PE at max. 160° C. under continuous gentleshaking in the autosampler of the GPC instrument.

The xylene soluble fraction at room temperature (XS, wt.-%): The amountof the polymer soluble in xylene is determined at 25° C. according toISO 16152; first edition; 2005-07-01.

Rheology: Dynamic rheological measurements were carried out withRheometrics RDA-II QC on compression moulded samples under nitrogenatmosphere at 230° C. using 25 mm-diameter plate and plate geometry. Theoscillatory shear experiments were done within the linear viscoelasticrange of strain at frequencies from 0.015 to 300 rad/s. (ISO 6721-10)The values of storage modulus (G′), loss modulus (G″), complex modulus(G′) and complex viscosity (η*) were obtained as a function of frequency(w).

The Zero shear viscosity (η₀) was calculated using complex fluiditydefined as the reciprocal of complex viscosity. Its real and imaginarypart are thus defined byf′(ω)=η′(ω)/[η′(ω)²+η″(ω)²] andf′(ω)=η″(ω)/[η′(ω)²+η″(ω)²]From the following equationsη′=G″/ω and η″=G′/ωf′(ω)=G″(ω)·ω/[G′(ω)² +G″(ω)²]f′(ω)=G′(ω)·ω/[G′(ω)² +G″(ω)²]

The complex viscosity ratio is the ratio of the complex viscosity (η*)obtained at 0.05 rad/sec to the complex viscosity (η*) obtained at 300rad/sec.

DSC analysis, melting temperature (T_(m)) and heat of fusion (H_(f)),crystallization temperature (T_(c)) and heat of crystallization (H_(c)):measured with a TA Instrument Q200 differential scanning calorimetry(DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357/part3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min inthe temperature range of −30 to +225° C. Crystallization temperature andheat of crystallization (H_(c)) are determined from the cooling step,while melting temperature and heat of fusion (H_(f)) are determined fromthe second heating step p.

The glass transition temperature Tg is determined by dynamic mechanicalanalysis according to ISO 6721-7. The measurements are done in torsionmode on compression moulded samples (40×10×1 mm³) between −100° C. and+150° C. with a heating rate of 2° C./min and a frequency of 1 Hz.

Tensile test: The tensile test (modulus, strength and tensile stress atbreak) is measured at 23° C. according to ISO 527-1 (cross head speed 1mm/min) using injection moulded specimens moulded at 180° C. or 200° C.according to ISO 527-2(1B), produced according to EN ISO 1873-2 (dog 10bone shape, 4 mm thickness).

Stepwise Isothermal Segregation Technique (SIST)

The isothermal crystallisation for SIST analysis was performed in aMettler TA820 DSC on 3±0.5 mg samples at decreasing temperatures between200° C. and 105° C.

(i) the samples were melted at 225° C. for 5 min.,

(ii) then cooled with 80° C./min to 145° C.

(iii) held for 2 hours at 145° C.,

(iv) then cooled with 80° C./min to 135° C.

(v) held for 2 hours at 135° C.,

(vi) then cooled with 80° C./min to 125° C.

(vii) held for 2 hours at 125° C.,

(viii) then cooled with 80° C./min to 115° C.

(ix) held for 2 hours at 115° C.,

(x) then cooled with 80° C./min to 105° C.

(xi) held for 2 hours at 105° C.

After the last step the sample was cooled down with 80° C./min to −10°C. and the melting curve was obtained by heating the cooled sample at aheating rate of 10° C./min up to 200° C. All measurements were performedin a nitrogen atmosphere. The melt enthalpy is recorded as function oftemperature and evaluated through measuring the melt enthalpy offractions melting within temperature intervals of

50 to 60° C.; 60 to 70° C.; 70 to 80° C.; 80 to 90° C.; 90 to 100° C.;100 to 110° C.; 110 to 120° C.; 120 to 130° C.; 130 to 140° C.; 140 to150° C.; 150 to 160° C.; 160 to 170° C.; 170 to 180° C.; 180 to 190° C.;190 to 200° C.

B. Examples

The catalyst used in the polymerization process for the polypropylene ofthe inventive examples (IE1 to IE6) and the comparative examples (CE1 toCE3) was the commercial Ziegler-Natta catalyst ZN168M (succinate asinternal donor, 2.5 wt.-% Ti) from Lyondell-Basell was used along withtriethyl-aluminium (TEAL) as co-catalyst and dicyclo pentyl dimethoxysilane (D-donor) as donor.

The aluminium to donor ratio, the aluminium to titanium ratio and thepolymerization conditions are indicated in table 1.

TABLE 1a Preparation of inventive propylene homopolymers 1E1 1E2 1E3 1E41E5 1E6 TEAL/Ti [mol/mol] 250 250 250 250 250 250 TEAL/Donor [mol/mol] 55 5 5 5 5 Donor/Ti [mol/mol] 50 50 50 50 50 50 LOOP time [min] 25 25 2525 25 25 temp [° C.] 75 75 75 75 75 75 split [wt.-%] 58.8 57.5 54.3 5759.2 54 MFR₂ [g/10′] 1003 550 415 550 550 550 H2/C3 [mol/kmol] 38.3 26.422.3 26.4 26.2 25.7 pressure [bar] 49.8 44.4 42.5 44.5 44.4 44 GPR1 time[min] 154 121 106 115 115 111 temp [° C.] 80 80 80 80 80 80 split[wt.-%] 36.1 36.8 36.2 36.4 36.3 36 MFR₂ [g/10′] 213 79 60 79 79 79H2/C3 [mol/kmol] 100 61 56 62 60 62 pressure [bar] 32 32 32 32 32 32GPR2 time [min] 161 173 136 140 175 243 temp [° C.] 80 80 80 80 70 80split [wt.-%] 5.1 5.7 9.5 6.6 4.5 10.0 MFR₂ [g/10′] × 10⁻⁴ 12 9 605 390.9 17 H2/C3 [mol/kmol] 2.0 1.3 3.2 2.2 2.2 2.3 pressure [bar] 32 32 3232 25 32 n.d. = not detectable

TABLE 2a Properties of inventive propylene homopolymers 1E1 1E2 1E3 1E41E5 1E6 XCS [wt %] 4.4 3.9 3.7 3.9 3.7 4.0 MFR₂ [g/10′] 286 126 89 124135 77 Mn [kg/mol] 10 12 13 12 10 7 Mw [kg/mol] 130 167 171 165 140 110Mz [kg/mol] 1267 1399 1128 1328 962 783 Mw/Mn [-] 13.0 13.9 13.2 13.814.0 15.7 Mz/Mw [-] 9.7 8.4 6.6 8.0 6.9 7.1 Mz/Mn [-] 126.7 116.6 86.8110.7 96.2 111.9 Eta*(0.05/300) [-] 7.6 9.8 9.7 11.7 — 12.8 Tm [° C.]161 162 163 162 161 — Tc [° C.] 120 120 119 121 118 118 2,1 e [%] n.d.n.d. n.d. n.d. n.d. n.d. mmmm [%] 96.2 96.0 96.5 96.3 96.9 — Tg [° C.]−9 −5 −4 −5 — — TM (180) [MPa] 2030 2033 1950 1983 — — TS (180) [MPa]28.8 35.3 35.4 32.5 — — TSB (180) [MPa] 28.7 35.3 35.3 32.5 — — n.d. =not detectable TM (180) tensile modulus measured on specimen inj.moulded at 180° C. TS (180) tensile strength measured on specimen inj.moulded at 180° C. TSB (180) tensile stress at break measured onspecimen inj. moulded at 180° C.

TABLE 3a Properties of inventive propylene homopolymers (containing 0.15wt.-% NA11UH) 1E1 1E2 1E3 1E4 1E5 1E6 Tm [° C.] 162 163 164 164 163  164 Tc [° C.] 134 134 134 134 132   132 Tg [° C.] −10 −8 −6 −8 — −6 TM(180) [MPa] 2318 2347 2299 2397 2183*   2377 TS (180) [MPa] 32.4 35.137.4 36.4  36.0* 38.7 TSB (180) [MPa] 32.4 35.1 37.3 36.4  36.0* 38.6n.d. = not detectable TM (180) tensile modulus measured on specimen inj.moulded at 180° C. (* at 200° C.) TS (180) tensile strength measured onspecimen inj. moulded at 180° C. (* at 200° C.) TSB (180) tensile stressat break measured on spec.inj. moulded at 180° C. (* at 200° C.) NA11 UH2,2′-methylenebis (4, 6,-di-tert-butylphenyl) phosphate

TABLE 4a SIST data of the inventive propylene homopolymers Temp. 1E1 1E21E3 1E4 1E5 1E6 Range/° C. [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] 90-100 0 0 0 0 0 0 100-110 0 0 0 0 0 0 110-120 0.51 0.16 0.35 0.21 — —120-130 0.71 0.69 0.81 0.79 — — 130-140 1.62 1.69 1.79 1.79 — — 140-1507.29 7.59 7.76 7.52 — — 150-160 29.21 28.34 27.89 27.44 — — 160-170 5554 53.6 52.74 — — 170-180 9.54 7.51 7.78 9.54 — — 180- 0 0 0 0 — — SISTratio 1.54 1.60 1.59 1.65 — — SIST ratio: the weight ratio of thecrystalline fractions melting in the temperature range of above 160 to180° C. to the crystalline fractions melting in the temperature range of90 to 160 [(>160-180)/(90-160)]

TABLE 5a SIST data of the inventive propylene homopolymers (containing0.15 wt.-% NA11UH) Temp. 1E1 1E2 1E3 1E4 1E5 1E6 Range/° C. [wt %] [wt%] [wt %] [wt %] [wt %] [wt %]  90-100 0 0.04 0.15 0 0 — 100-110 0.030.09 0.21 0 0 — 110-120 0.39 0.42 0.54 0.27 0.22 — 120-130 1.12 1.111.19 0.95 0.8 — 130-140 2.32 2.2 2.24 1.99 1.83 — 140-150 4.89 4.6 4.644.41 4.3 — 150-160 15.09 14.06 14.3 14.03 14.15 — 160-170 65.54 57.0956.88 58.97 60.2 — 170-180 10.62 20.39 19.81 19.38 18.48 — 180- 0 0 0 00 — SIST ratio 3.19 3.44 3.29 3.62 3.69 — SIST ratio: the weight ratioof the crystalline fractions melting in the temperature range of above160 to 180° C. to the crystalline fractions melting in the temperaturerange of 90 to 160 [(>160-180)/(90-160)]

TABLE 1b Preparation of comparative propylene homopolymers CE1 CE2 CE3TEAL/Ti [mol/mol] 250 250 250 TEAL/Donor [mol/mol] 5 5 5 Donor/Ti[mol/mol] 50 50 50 LOOP time [min] 25 25 25 temp [° C.] 75 75 75 split[wt.-%] 100 56 59 MFR₂ [g/10′] 417 1003 1003 H2/C3 [mol/kmol] 22.5 3837.6 pressure [bar] 80 80 80 GPR1 time [min] — 154 175 temp [° C.] — 8080 split [wt.-%] — 44 41 MFR₂ [g/10′] — 79 313 H2/C3 [mol/kmol] — 59 100pressure [bar] — 32 32 n.d. = not detectable

TABLE 2b Properties of comparative propylene homopolymers CE1 CE2 CE3XCS [wt %] 4.8 4.2 4.6 MFR₂ [g/10′] 494 355 627 Mn [kg/mol] 9 10 9 Mw[kg/mol] 106 110 92 Mz [kg/mol] 793 690 541 Mw/Mn [−] 11.8 11.0 10.2Mz/Mw [−] 7.5 6.3 5.9 Mz/Mn [−] 88 69 60 Eta * (0.05/300) [−] — 2.8 — Tm[° C.] 160 162 160 Tc [° C.] 121 121 121 2,1 e [%] n.d. n.d. n.d. mmmm[%] 96.3 96.6 96.4 Tg [° C.] −8 −9 −11 TM (180) [MPa] 1895 1885 1930 TS(180) [MPa] 27.1 28.6 26.3 TSB (180) [MPa] 27.0 28.5 26.2 n.d. = notdetectable TM (180) tensile modulus on specimen inj. moulded at 180° C.TS (180) tensile strength on specimen inj. moulded at 180° C. TSB (180)tensile stress at break on specimen inj. moulded at 180° C.

TABLE 3b Properties of comparative propylene homopolymers (containing0.15 wt.-% NA11UH) CE1 CE2 CE3 Tm [° C.] — 162 162 Tc [° C.] — 134 134Tg [° C.] — — — TM (180) [MPa] — 2185 2161 TS (180) [MPa] — 28.6 30.7TSB (180) [MPa] — 28.6 30.7 n.d. = not detectable TM (180) tensilemodulus on specimen inj. moulded at 180° C. TS (180) tensile strength onspecimen inj. moulded at 180° C. TSB (180) tensile stress at break onspecimen inj. moulded at 180° C. NA11UH 2,2′-methylenebis(4,6,-di-tert-butylphenyl) phosphate

TABLE 4b SIST data of the comparative propylene homopolymers CE1 CE2 CE3Temp. Range/° C. [wt %] [wt %] [wt %]  90-100 0 0 0 100-110 0 0 0.22110-120 0.26 0.29 0.34 120-130 0.87 0.92 0.88 130-140 2.01 2.03 1.95140-150 8.04 7.85 7.84 150-160 32.61 29.61 31.75 160-170 53.67 54.2652.01 170-180 2.53 5.04 5 180- 0 0 0 SIST ratio 1.28 1.46 1.33

TABLE 5b SIST data of the comparative propylene homopolymers (containing0.15 wt.-% NA11UH) CE1 CE2 CE3 Temp. Range/° C. [wt %] [wt %] [wt %] 90-100 — — — 100-110 — 0.04 — 110-120 — 0.4 0.29 120-130 — 1.15 1.05130-140 — 2.36 2.29 140-150 — 4.94 4.88 150-160 — 15.43 15.4 160-170 —67.14 65.76 170-180 — 8.56 10.3 180- — 0 0 SIST ratio — 3.11 3.18

The invention claimed is:
 1. A propylene homopolymer having: (a) a meltflow rate MFR₂ (230° C.) measured according to ISO 1133 of 60 to 500g/10 min; (b) a ratio of weight average molecular weight (Mw) to numberaverage molecular weight (Mn) [Mw/Mn] of at least 12.0; and (c) a xylenecold soluble content (XCS) determined according ISO 16152 (25° C.) of2.5 to 4.5 wt. %.
 2. The propylene homopolymer according to claim 1,wherein the propylene homopolymer has a ratio of the complex viscosityeta* at 0.05 rad/sec to the complex viscosity eta* at 300 rad/sec of atleast 4.0.
 3. The propylene homopolymer according to claim 1, whereinthe propylene homopolymer has: (a) 2,1 erythro regio-defects of equal orbelow 0.4 mol. % determined by ¹³C-NMR spectroscopy; and/or (b) a pentadisotacticity (mmmm) of more than 95.0%.
 4. The propylene homopolymeraccording to claim 1, wherein the propylene homopolymer has: (a) a ratioof z-average molecular weight (Mz) to weight average molecular weight(Mw) [Mz/Mw] of at least 6.0; and/or (b) a ratio of z-average molecularweight (Mz) to number average molecular weight (Mn) [Mz/Mn] of at least80.
 5. The propylene homopolymer according to claim 1, wherein thepropylene homopolymer is not nucleated and optionally has: (a) a weightratio of the crystalline fractions melting in the temperature range ofabove 160 to 180° C. to the crystalline fractions melting in thetemperature range of 90 to 160° C. of at least 1.30, wherein thefractions are determined by a stepwise isothermal segregation technique(SIST), and/or (b) a crystallization temperature of at least 112° C.;and/or (c) a tensile modulus measured according to ISO 527-2 of at least1,950 MPa.
 6. The propylene homopolymer according to claim 2, whereinthe propylene homopolymer is α-nucleated and optionally has: (a) aweight ratio of the crystalline fractions melting in the temperaturerange of above 160 to 180° C. to the crystalline fractions melting inthe temperature range of 90 to 160° C. of at least 2.90, wherein thefractions are determined by a stepwise isothermal segregation technique(SIST); and/or (b) a crystallization temperature of at least 128° C.;and/or (c) a tensile modulus measured according to ISO 527-2 of at least2,150 MPa.
 7. The propylene homopolymer according to claim 1, whereinthe propylene homopolymer has a melting temperature Tm of more than 160°C.
 8. The propylene homopolymer according to claim 1, wherein thepropylene homopolymer (H-PP) has a first propylene homopolymer fraction(H-PP1), a second propylene homopolymer fraction (H-PP2) and a thirdpropylene homopolymer fraction (H-PP3), the first propylene homopolymerfraction (H-PP1), second propylene homopolymer fraction (H-PP2) andthird propylene homopolymer fraction (H-PP3) differ in the melt flowrate MFR₂ (230° C.) by at least 30 g/10 min.
 9. The propylenehomopolymer according to claim 8, wherein: (a) the melt flow rate MFR₂(230° C.) of the first propylene homopolymer fraction (H-PP1) is atleast 4 times higher than the melt flow rate MFR₂ (230° C.) of thesecond propylene homopolymer fraction (H-PP2); and/or (b) the melt flowrate MFR₂ (230° C.) of the second propylene homopolymer fraction (H-PP2)is at least 1000 times higher than the melt flow rate MFR₂ (230° C.) ofthe third propylene homopolymer fraction (H-PP3).
 10. The propylenehomopolymer according to claim 8, wherein: (a) the melt flow rate MFR₂(230° C.) of the first propylene homopolymer fraction (H-PP1) is atleast 300 g/10 min; and/or (b) the melt flow rate MFR₂ (230° C.) of thesecond propylene homopolymer fraction (H-PP2) is in the range of 10.0 tobelow 300 g/10 min; and/or (c) the melt flow rate MFR₂ (230° C.) of thethird propylene homopolymer fraction (H-PP3) is below 0.1 g/10 min. 11.The propylene homopolymer according claim 6, wherein the amount: (a) ofthe first propylene homopolymer fraction (H-PP1) is in the range of 40to 60 wt. %, (b) of the second propylene homopolymer fraction (H-PP2) isin the range of 25 to 59.0 wt. %, and (c) of the third propylenehomopolymer fraction (H-PP3) is in the range of 1.0 to 15.0 wt. %, basedon the total amount of the propylene homopolymer.
 12. A process for themanufacture of a propylene homopolymer accordingly to claim 1, in asequential polymerization system that includes at least threepolymerization reactors (R1), (R2) and (R3) connected in series, theprocess comprising: polymerizing propylene in the at least threepolymerization reactors (R1), (R2) and (R3) in the presence of: (a) aZiegler-Natta catalyst (ZN-C) comprising a titanium compound (TC) havingat least one titanium-halogen bond, and an internal donor (ID), bothsupported on a magnesium halide, (b) a co-catalyst (Co), and (c) anexternal donor (ED), wherein: the internal donor (ID) comprises at least80 wt. % of a succinate; the molar-ratio of co-catalyst (Co) to externaldonor (ED) [Co/ED] is 2 to 60; and the molar-ratio of co-catalyst (Co)to titanium compound (TC) [Co/TC] is 150 to
 300. 13. The processaccording to claim 12, wherein: (a) the molar-ratio of external donor(ED) to titanium compound [ED/TC] is in the range of more than 5 tobelow 100; and/or (b) the first polymerization reactor (R1) is a loopreactor (LR), the second polymerization reactor is a first gas phasereactor (GPR1) and the third polymerization reactor is a second gasphase reactor (GPR2).
 14. The process according to claim 12, wherein:(a) the operating temperature in the first polymerization reactor (R1)is in the range of 70 to 85° C.; and/or (b) the operating temperature inthe second polymerization reactor (R2) is in the range of 70 to 95° C.;and/or (c) the operating temperature in the third polymerization reactor(R3) is in the range of 70 to 95° C.
 15. The process according to claim12, wherein: (a) the total average residence time is at most 500 min;and/or (b) the average residence time in the polymerization firstreactor (R1) is at least 20 min; and/or (c) the average residence timein the second polymerization reactor (R2) is at least 90 min; and/or (d)the average residence time in the third polymerization reactor (R3) isat least 100 min.
 16. A propylene homopolymer produced by the processaccording to claim 12.